Effects of saline drinking on malignant course of renal hypertension in rats

In rats with unilateral renal artery stenosis and an intact contralateral kidney, a malignant course of hypertension (MH) may develop, which is characterized by 1) high BP levels, 2) sodium and water loss and a polyuric-polydipsic syndrome, 3) marked activation of the renin-angiotensin system, 4) malignant nephrosclerosis in the contralateral kidney and high plasma urea concentrations, and 5) deterioration of the animals' general condition. (Some rats exhibit signs of a cerebral vascular crisis; some rats die). When such rats are offered in addition to water 0.9% NaCl, they compulsively drink the saline, BP falls for some days to levels found in the other hypertensive animals, and signs of MH nearly or completely disappear. It is concluded that high saline intake has, for a limited period, a beneficial effect on the malignant course of renal hypertension in rats. The observations made are consistent with the hypothesis that salt and water loss, which ensue subsequent to an increase of BP into a critical high range might trigger the onset of malignant hypertension.